Method for modifying graft polyolefins, compositions and articles comprising polyolefins thus modified

ABSTRACT

Process for modifying a polyolefin grafted with acid or anhydride groups, by at least partial neutralization of these groups with at least one neutralizing agent comprising an organic salt (1) that releases an organic acid (I) during the neutralization, according to which the organic acid (I) derived from the neutralization of the grafted polyolefin is reacted with at least one inorganic salt (2). 
     Modified polyolefin (that can be) obtained by the process described above. 
     Polymeric composition containing (A) at least one polymer, and (B) at least one modified polyolefin (that can be) obtained by the process above. 
     Article comprising the modified polyolefin or the composition described above.

The present invention relates to a process for modifying graftedpolyolefins, and also to the resulting polyolefins.

A problem often posed by polymers in general, and polyolefins inparticular, is their insufficient melt strength during their processingby extrusion.

It is well known that the melt strength of polyethylene (PE), butespecially of polypropylene (PP), defined by a high elongationalviscosity, is insufficient for certain types of processing, such asextrusion foaming, extrusion blow-moulding, thermoforming andblow-moulding, in particular 3D blow-moulding. In addition, for certainapplications such as foaming and adhesion, for example, it may prove tobe advantageous for the viscosity to increase (in particularexponentially) as a function of time. This phenomenon is calledelongational hardening (EH).

Solutions proposed in order to solve this problem consist in branchingthe macromolecular structure of the PE or PP by creating covalent bondsbetween the macromolecules. However, in practice, branched resinsproduced by covalent coupling all suffer from a tendency for thebranching to degrade under the influence of the shear inherent in theprocessing. In addition, substantial irreversible covalent branching (orcrosslinking) results in breaks in flow that limit productivity and/orthe quality of the finished product.

In order to be able to increase the connection density betweenmacromolecules without being limited by the crosslinking, it is possibleto introduce a substantial portion of the branchings via reversibleionic bonds. This makes it possible to increase the melt strength whileat the same time maintaining the thermoplastic nature, and also makes itpossible, under correctly chosen conditions, to obtain EH.

Thus, application WO 00/66641 in the name of Solvay describes a processaccording to which a polyolefin grafted using a carbonyl and/or an acidanhydride, from which the “free” (non-grafted) grafting monomer has beenremoved beforehand, is subjected to neutralization with at least onecompound comprising alkali metal cations, alkaline earth metal cationsand transition metal cations. This process has the advantage ofproviding a non-crosslinked resin (typically having a content ofproducts insoluble in xylene at 130° C. of less than 1%) having, despiteeverything, a high level of EH. However, it has the disadvantage ofproviding resins whose fluidity is difficult to optimize, i.e. ofproducing either resins that are relatively fluid (with a relativelyhigh MFI), the melt strength of which is insufficient for certainapplications, or resins having an MFI that is too low, or even virtuallyzero, which are no longer capable of melt processing.

In addition, according to a preferred variant of this invention, theproducts of the neutralization reaction (organic acid in the case of theuse of organic salts as neutralizing agents) are removed from thefinished product by stripping or by degassing in order to shift theequilibrium of the neutralization reaction. However, the applicant hasnoted that the removal of neutralization by-products is difficult andincomplete in the case of organic acids such as acetic acid, forexample. Now, the use of organic metal salts as neutralizing agentsoften gives good results in terms of elongational hardening. It shouldalso be noted that certain organic acids (such as acetic acid and lacticacid, for example) can lead to the finished product having an unpleasantsmell, and to organoleptic problems. Filially, the use of organic metalsalts also induces, in certain cases, a yellowing that is undesirablefrom an aesthetic point of view, which yellowing is accentuated duringsubsequent processing.

The aim of the present invention is consequently to propose a processfor modifying grafted polyolefins exhibiting improved properties withregard especially to the melt strength, and in particular to the meltviscosity, and which makes it possible, in certain cases, to improve theorganoleptic properties, the colour and the odour of these polyolefins.

To this effect, the present invention relates to a process for modifyinga polyolefin grafted with acid or anhydride groups, by at least partialneutralization of these groups with at least one neutralizing agentcomprising an organic salt (1) that releases an organic acid (I) duringthe neutralization, according to which the organic acid (I) derived fromthe neutralization of the grafted polyolefin is reacted with at leastone inorganic salt (2) [process (P)].

The modified polyolefins obtained by means of the process (P) inaccordance with the present invention [modified polyolefins (B1)]exhibit improved properties by virtue of the use of the inorganic salt(2). In fact, first of all, the use of this inorganic salt (2) makes itpossible to remedy the abovementioned problems of yellowing. Next, thereaction of the inorganic salt (2) with the organic acid (I) forms,firstly, an inorganic acid (II) which can be partially eliminated bystripping or degassing and, secondly, an organic salt (3) which does notdisturb the proper functioning of the process and even, in certain cases(according to the choice of reactants: see below), makes it possible toimprove it. The fact that the organic acid is eliminated from the systemmakes it possible at the same time to eliminate the organolepticproblems. In addition, the fact that this acid is eliminated shifts theequilibrium of the reaction to neutralize the acid or anhydridefunctions and therefore promotes this neutralization. This advantage(shift in equilibrium reaction) can even be accentuated with the choiceof reactants (organic (1) and inorganic (2) salts) resulting in anorganic salt (3) which is eliminated from the reaction medium (either byprecipitation, or by chemical reaction with certain compounds present inthe reaction medium). The adjusting of several reactants therefore makesit possible to readily promote the neutralization reaction. Finally, theapplicant has noted that adding an inorganic salt after or at the sametime as an organic salt makes it possible to reduce the size of theresidual aggregates of inorganic salt and, in doing so, to improve themechanical properties of the modified polyolefin obtained. Theseaggregates are in fact generally less than 500 nm, or less than 300 nm,and even less than 100 nm in size, which is clearly finer than theaggregates of inorganic salt obtained when said salt is used alone asneutralizing agent.

The polyolefins that can be used in the process according to theinvention are polymers of linear olefins containing from 2 to 8 carbonatoms, such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene and1-octene, and they are grafted with acid or anhydride functions, forexample by the free-radical process. These olefins preferably containfrom 2 to 6 carbon atoms, more particularly from 2 to 4 carbon atoms.They can be selected from homopolymers of the abovementioned olefins andfrom copolymers of these olefins, in particular copolymers of ethyleneor of propylene with one or more comonomers, and also from blends ofsuch polymers. The comonomers are advantageously chosen from the olefinsdescribed above, from diolefins comprising from 4 to 18 carbon atoms,such as 4-vinylcyclohexene, dicyclopentadiene, methylene norbornene andethylidene norbornene, 1,3-butadiene, isoprene or 1,3-pentadiene, andfrom styrene monomers such as styrene and alpha-methylstyrene. Thecontent of weight of units formed from the comonomers in the polyolefinsis advantageously less than 50%, preferably less than 30%, andparticularly preferably less than 10% by weight. It is understood thatthe term “polyolefin” is equally intended to denote the polymers asdescribed above taken in isolation, and blends thereof.

Preferably, the polyolefin is chosen from polymers of ethylene and/or ofpropylene (i.e. the polyolefin comprises repeat units derived fromethylene and/or from propylene). Particularly preferably, the polyolefinis chosen from (i) ethylene homopolymers, (ii) propylene homopolymers,(iii) copolymers composed of repeat units derived from ethylene and frompropylene, (iv) terpolymers composed of repeat units derived fromethylene, from propylene and from a diolefin comprising from 4 to 18carbon atoms commonly called EPDM rubbers, and also (v) blends of theabovementioned polyolefins with one another. The propylene homopolymersand the copolymers composed predominantly (by weight) of repeat unitsderived from propylene and to a minor extent (by weight) of repeat unitsderived from ethylene are most particularly preferred.

According to a particular embodiment of the process in accordance withthe invention, the polyolefin is block copolymer, preferably a blockcopolymer comprising repeat units derived from ethylene and/or frompropylene. By way of examples of block copolymers, mention may be madeof AB diblock copolymers and ABA triblock copolymers, where the A blocksare blocks of polystyrene homopolymer and the B block are blocks of acopolymer composed, firstly, of repeat units derived from ethylene and,secondly, of repeat units derived from propylene and/or from a diolefincomprising from 4 to 18 carbon atoms, such as butadiene, that areoptionally hydrogenated (for example, the repeat units derived frombutadiene may be hydrogenated to butylene repeat units). According tothis particular method of implementing of the process according to theinvention, and by exception, the content by weight of units formed fromcomonomers other than ethylene and propylene is advantageously at least10%, preferably at least 20% by weight; in addition, it isadvantageously less than 75%, and preferably less than 50% by weight.

According to the present invention, the grafted polyolefin is preferablysemicrystalline, i.e. it has at least one melting point.

The acid or anhydride groups that are grafted onto these polyolefins aregenerally chosen from unsaturated mono- or dicarboxylic acids and theirderivatives, and unsaturated mono- or dicarboxylic acid anhydrides andtheir derivatives. These groups preferably comprise from 3 to 20 carbonatoms. As typical examples, mention may be made of acrylic acid,methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonicacid, citraconic acid, maleic anhydride, itaconic anhydride, crotonicanhydride and citraconic anhydride. Maleic anhydride is mostparticularly preferred. In particular, it gives good results in the caseof polymers of ethylene and/or of propylene.

The amount of acid or anhydride groups grafted is generally sufficientto allow an improvement in the properties (melt strength and EH) of thegrafted polyolefin; it is generally greater than or equal to 0.01% byweight relative to the polyolefins, or even greater than or equal to0.02% by weight, or better still greater than or equal to 0.03% byweight. In practice, this amount is, however, generally less than orequal to 2.0% by weight, preferably less than or equal to 1.5%, andbetter still less than or equal to 1.0% by weight. In fact, the graftingof the acid or anhydride groups is generally initiated by a radicalgenerator, the amount of which should be limited so as to avoid havingto deal with a resin that is too fluid in the case of a propylenepolymer, or not fluid enough in the case of an ethylene polymer. Asradical generators that are normally used, mention may be made oft-butylcumyl peroxide, 1,3-di(2-t-butylperoxyisopropyl)benzene,2,5-dimethyl-2,5-di(t-butylperoxy)hexane, di(t-butyl)peroxide and2,5-dimethyl-2,5-di(t-butylperoxy)-3-hexyne.2,5-dimethyl-2,5-di-t-butylperoxyhexane (DHBP) gives rise to graftedpolyolefins that give good results in the process according to thepresent invention.

The grafted polymers that can be used in the process according to theinvention are most commonly chosen from homopolymers and copolymers ofethylene and/or of propylene, the melt flow index (MFI) of which isgreater than or equal to 1, preferably greater than or equal to 5,particularly preferably greater than or equal to 10. The MFI of theseresins is, however, generally less than or equal to 5000 dg/min,preferably less than or equal to 4000 dg/min, particularly preferablyless than or equal to 3000 dg/min. The MFI of the polyolefins ismeasured at 230° C. under a weight of 2.16 kg for propylene polymersaccording to ASTM standard D 1238 (1986) and at 190° C. under a weightof 5 kg for ethylene polymers according to ISO standard 1133 (1991).

The grafted polyolefins according to the present invention preferablycontain little free (non-grafted) monomer, for example an amount lessthan or equal to 500 ppm, or even less than or equal to 400 ppm, orbetter still less than or equal to 200 ppm.

According to the invention, the neutralization of the acid or anhydridegroups is carried out with at least one neutralizing agent comprising anorganic salt. Preferably, this organic salt is a salt that is liquid atthe processing temperature. The applicant has in fact noted that suchsalts give better results in terms of reactivity. Examples of salts thatare liquid at the usual processing temperatures are Li acetate and Liformate (respective melting points (T_(m)) of 53-56° C. and 94° C.), Mgacetate (T_(m)=72-75° C.), K formate (T_(m)=165-168° C.), Zn acetate andZn stearate (T_(m)=237° C. and 128-130° C.), Cu acetate (T_(m)=115° C.),Na lactate and Na formate (T_(m) less than ambient temperature and equalto 261° C. respectively), ammonium acetate and ammonium formate(T_(m)=112-114 and 119-121° C.). Zn acetate and Na lactate give goodresults, in particular respectively with polymers of ethylene and/or ofpropylene.

In the process according to the invention, the organic salt and theinorganic salt can be introduced either at the same time, or in adeferred way. Simultaneous introduction is preferred when the organicsalt is Na lactate, whereas deferred introduction (organic salt theninorganic salt) is preferred in the case of Zn acetate. This is becausethe latter is unstable in an aqueous solution with a pH of greater than4 (precipitation of Zn(OH)₂) and is therefore preferably introduced inan acidic solution and not in a basic solution.

The amount of organic salt added depends on its nature, on the nature ofthe grafted polyolefin and on the envisaged use (and therefore on thedesired properties) of the modified polyolefin. Those skilled in the artcan readily optimize, by experiment, the amount of salt according tothese parameters. However, the organic salt is generally used in anamount that is approximately the stoichiometric value relative to theacid or anhydride groups. In the case of propylene polymers, the amountof organic salt added will generally be greater than or equal to 0.5molar equivalent (mol. eq.) relative to the number of acid or anhydridefunctions, or even greater than or equal to 0.75 mol. eq., and incertain cases, greater than or equal to 1 mol. eq. In the case ofethylene polymers, this amount will generally be less than or equal to 3mol. eq., or even less than or equal to 2 mol. eq., and preferably lessthan or equal to 1.5 mol. eq.

The organic salt is generally introduced into the grafted polyolefin inthe form of an aqueous solution, which is moreover particularlyadvantageous in the case of polyolefins grafted with anhydridefunctions. This is because the water contained in this solution is thenused for the hydrolysis of this anhydride to a diacid, which is the formthat effectively reacts with the organic salt so as to release thecorresponding organic acid.

The inorganic salt (2) that serves to capture the organic acid (I) inthe process according to the invention is preferably, as explainedpreviously, chosen according to the nature of the organic salt (1) andof the organic acid (I), so as to give, respectively, an inorganic acid(II) and an organic salt (3) that are readily eliminated from thereaction medium. Thus, care will preferably be taken to ensure that theinorganic acid (II) is a very volatile and/or unstable acid thatdecomposes at the processing temperature so as to release at least onegas (for instance carbonic acid) and, in so doing, shift the equilibriumof the reaction between the organic acid (I) and the inorganic salt (2).Similarly, care will preferably be taken to ensure that the organic salt(3) is eliminated from the reaction medium by any means (it may, forexample, either be insoluble at the processing temperature, or may beidentical to the organic salt (1), in which case it will react with theacid or anhydride functions not yet neutralized on the graftedpolyolefin).

The inorganic salts (2) may be liquid at the processing temperature;however, good results have been obtained with solid salts. Inorganicsalts that are suitable for the process according to the invention arealkali metal carbonates, alkaline earth metal carbonates and rare earthmetal carbonates, and in particular Na carbonate and K carbonate. Nacarbonate gives good results, in particular when the organic salt usedis Zn acetate or an Na lactate. It makes it possible in particular toremedy the organoleptic problems and to decrease the yellowing in aparticularly effective manner.

The amount of inorganic salt (2) added should be sufficient toneutralize the organic acid released. Thus, an amount of less than orequal to 5 mol. eq., or even less than or equal to 4 mol. eq., andpreferably less than or equal to 3 mol. eq., relative to the number ofacid or anhydride functions of the grafted polyolefin, will preferablybe added.

The inorganic salt (2) is preferably also introduced into the graftedpolyolefin in the form of an aqueous solution, still so as to benefitfrom the effect of hydrolysis of the water on the anhydride functions,where appropriate.

Care will be taken to optimize the concentration of the aqueoussolutions of organic and inorganic salts so as to prevent precipitationof solid particles in the device for introducing these solutions intothe grafted polyolefin, while at the same time limiting as much aspossible to amount of water (since the latter must subsequently beeliminated).

In order to carry out the process according to the present invention,all the devices (“reactors”) known for this purpose can be used. Thus,it is possible to work, without distinction, with external mixers orinternal mixers, or static mixers. Internal mixers are most suitableand, among these, Brabender® batch mixers and continuous mixers, such asextruders, that consist mainly of at least one screw rotating in abarrel. In the process according to the invention, the extruder that canbe used may be a single-screw extruder, or a counter-rotating orco-rotating twin-screw extruder, of self-cleaning type. Self-cleaningtwin-screw extruders give good results.

An extruder within the meaning of this variant of the present inventioncomprises at least, in order, the following components: a feed zone, amelt zone, a reactant injection zone, a homogenization/reaction zone, adegassing zone and a zone for extracting the melt. Preferably, thedegassing zone comprises two vents: a first for degassing underatmospheric pressure and a second for stronger degassing, under vacuum.Preferably, the latter degassing is carried out under a high vacuum, forexample less than 10 mbar, or even less than 5 mbar, a maximum value of2 mbar giving good results. The organic salt is generally introducedinto the injection zone and, in the case of deferred introduction of aninorganic salt, the latter is advantageously introduced between the twodegassing vents. The extraction zone may also be followed by agranulator or a device that gives the extruded material a given form(film for example).

An extruder that is particularly preferred for carrying out the processaccording to the invention is made of a corrosion-resistant alloy. Aparticularly preferred alloy is an alloy consisting predominantly ofnickel or of cobalt.

In the process according to the invention, the organic and inorganicsalts are introduced into the injection zone(s) by any known device.Preferably, they are introduced using a high-pressure injector which ispreferably based on a corrosion-resistant alloy as described above.

In the process according to the invention, the grafted polyolefin may befed into the chosen reactor by any known means. In the case of anextruder, it may be fed into the feed zone by means of a weigh feeder.Alternatively, it may be fed in melt form via another extruder, forexample the one in which the grafting was carried out by reactiveextrusion. Finally, the grafting by reactive extrusion and the modifyingof the grafted polyolefin can take place in the same extruder. However,the latter two variants have the drawback of reducing production ratessince, where appropriate, the free monomer than has to be removed fromthe grafted polyolefin on line.

The temperature at which the process according to the invention iscarried out is generally above the melting point and below thedecomposition temperature of the grafted polyolefin, and preferablyabove the melting point of the organic salt in the zone where the latterreacts with the grafted polyolefin. This temperature will generally beat least 180° C., most commonly at least 190° C., in particular at least200° C. Generally, the process is carried out at a temperature notexceeding 400° C., most commonly not exceeding 300° C. and moreparticularly not exceeding 250° C.

The amount of time required to carry out the process in accordance withthe invention is generally from 10 seconds to 10 minutes, or even from30 seconds to 5 minutes.

In the course of the process, one or more usual polyolefin additives,such as for example stabilizers, antioxidants, antistatic agents,organic dyes or mineral pigments, and fillers, etc., may be incorporatedat any moment, provided that they do not interfere with theneutralization of the acid or anhydride groups. Preferably, andprecisely so as to avoid this interference, when the process takes placein an extruder, the possible additive(s) will be added after the seconddegassing, just before the outlet.

In a preferred method of implementing the process according to theinvention, at least one stabilizer is added during the process.Preferably, the stabilizer used in this variant of the process accordingto the present invention is chosen from compounds comprising asterically hindered phenol group, from phosphorus compounds and frommixtures thereof. These are, for example, substances such as1,3,5-trimethyl-2,4,6-tris(3,5-t-butyl-4-hydroxybenzyl)benzene,pentaerythritol tetrakis-(3,5-di-t-butyl-4-hydroxy-phenylpropionate) ortris-(2,4-di-t-butylphenyl)phosphite, or the mixture of pentaerythrityltetrakis-(3,5-di-t-butyl-4-hydroxyphenylpropionate) and oftris-(2,4-di-t-butylphenyl)phosphite, preferably in equal amounts. Thepreferred stabilizer is1,3,5-trimethyl-2,4,6-tris(3,54-butyl-4-hydroxybenzyl)benzene.

The present invention also relates to modified polyolefins (PO) forwhose production the process according to the invention is particularlysuitable. The applicant has in fact noted that the process according tothe invention makes it possible to obtain modified polyolefinscomprising acid or anhydride groups with a high degree ofneutralization, exhibiting a particularly improved melt strengthcharacterized by an exponential increase in elongational viscosity(elongational hardening or EH) and by an ideal MFI (less than a givenvalue), while at the same time having little or no crosslinking (i.e.having a content of products insoluble in xylene at 130° C. of less than1%). According to this variant of the invention, the terra “elongationalhardening” is intended to denote an exponential increase in theelongational viscosity (expressed in kPa·S) measured in the molten state(in particular at 190° C. for PE resins and at 230° C. for PP resins),as a function of time (expressed in s) and for an elongation rate(expressed in s⁻¹) of 1. In general, the elongational viscosity of themodified polyolefins according to the invention ranges from less than 20to several hundred, or even to more than 1000 kPa·s, after 2 to 3 s.

This combination of properties is exceptional and is related, firstly,to the fact that organic acid (I), that plays the role of plasticizer athigh doses, is eliminated by reaction with the inorganic salt (2); and,secondly, to an increased content of ionic aggregates.

Consequently, the present invention also relates to the modifiedpolyolefins that can be obtained by a process as described above,comprising acid or anhydride groups that are at least partiallyneutralized by metal ions, and exhibiting:

a content of products insoluble in xylene at 130° C. of less than 1%,

an exponential increase in elongational viscosity as a function of time,

an MFI of less than or equal to 6 dg/min

[Modified Polyolefins (B2)].

The content of products insoluble in xylene at 130° C. can be determinedby any known method. A suitable method consists in dissolving 10 g ofthe polyolefin in granule form in 300 ml of xylene and refluxing thewhole for 2 h. The content of insoluble products is less than 1% whenthe solution obtained is completely transparent (i.e. no cloudy zones).

The modified polyolefins according to the invention have an MFI of lessthan or equal to 6, or even less than or equal to 5 dg/min. However, inorder for it to remain possible to process them, their MFI willgenerally be greater than or equal to 0.01 dg/min, or even greater thanor equal to 0.1 dg/min.

They generally also have a degree of neutralization of the acid oranhydride functions of greater than or equal to 40%, or even greaterthan or equal to 50% and, in certain cases, greater than or equal to70%. This degree of neutralization is, however, less than or equal to100%, generally less than or equal to 90%. This degree of neutralizationcan be measured by any known method. A method which gives good resultsconsists in analysing the sample by IR before and after neutralization,in the knowledge that the grafted maleic anhydride in its non-hydrolysedform exhibits an adsorption band around 1790 cm⁻¹, the grafted maleicanhydride in its hydrolysed form has an adsorption band around 1725 cm⁻¹and the grafted maleic anhydride in its neutralized form has one about1580 cm⁻¹.

Although these resins exhibit a high degree of neutralization, theircation content is however low. Thus, for a cation of given nature, it isgenerally less than or equal to 1% by weight, or even less than or equalto 0.8% by weight (relative to the total weight of the modifiedpolyolefin). This content may even, in certain cases be less than orequal to 0.7% in the case of Na⁺ ions and less than or equal to 0.5% inthe case of Zn⁺⁺ ions.

The modified polyolefins according to the invention have propertiessimilar to those of the base polyolefins (whether or not they aregrafted) and in particular very similar temperature resistance andcrystalline properties (melting point (T_(m)) and crystallizationtemperature in particular, measured by the DSC (Differential ScanningCalorimetry) technique according to standard ISO FDIS 11357-3 (1999), atthe second pass and with a scanning rate of 10 K/min). This implies thatthe difference between the T_(m) of a grafted resin and that of itsnon-grafted homologue is generally less than or equal to 5° C., or evenless than or equal to 3° C. Taking polymers of ethylene and/or ofpropylene as the starting point, this generally implies a T_(m) ofgreater than 100° C.

In addition, the modified polyolefins according to the invention exhibitimproved mechanical properties compared with the base polyolefins. Thus,in the case of PP homopolymer-based modified polyolefins, their tensilemodulus E (measured at 23° C. according to standard ISO 527-1) isgenerally greater than or equal to 2000 MPa, and in the case of HDPE(high density polyethylene)-based modified resins, said modulus isgreater than or equal to 1000 MPa. In addition, in the case of the PPhomopolymer-based modified polyolefins, a clear improvement inmechanical strength is observed, which results in a DTUL (DeflectionTemperature Under Load measured according to standard ISO 75-2 (9/1993))of greater than or equal to 120° C. under a load of 0.45 MPa and greaterthan or equal to 60° C. under a load of 1.8 MPa. Finally, the creepresistance of the modified polyolefins is substantially improvedcompared with that of the base resins; thus for example, whenmeasurements are carried out at 80° C. and under a load of 5 MPa, themodified polyolefins according to the invention generally exhibit adeformation after 100 h that is at least 15%, or at least 20%, and evenat least 25% less than those of the base polyolefins.

The modified polyolefins according to the invention also generallyexhibit an exceptional oxidation resistance (measured according to thePIO2 test). The PIO2 test for oxidation resistance consists in:

-   -   taking 20 nag of resin in the form of a pellet,    -   thermoregulating this pellet at the desired temperature (in        particular at 190° C. for the propylene-based polyolefins and at        210° C. for the ethylene-based polyolefins) under a stream of        nitrogen,    -   starting the measurement at time t₀ under a stream of oxygen,    -   measuring the amount of time required (in minutes) for the resin        to begin degrading (oxidizing), i.e. the amount of time required        for the appearance of an exotherm.

The PP-based modified polyolefins according to the prior art have a PI02of less than 60 min, whereas the PP-based modified polyolefins accordingto the invention can have a PI02 of greater than or equal to 60 min, incertain cases even greater than or equal to 70 min, or even greater thanor equal to 80 min. In the case of the PE-based modified polyolefinsaccording to the invention, they have a PI02 that is generally greaterthan or equal to 50 min, or greater than or equal to 60 min, or evengreater than or equal to 75 min.

Finally, it should be noted that, as already mentioned above, themodified polyolefins according to the invention exhibit an improvementin terms of organoleptic properties and in terms of yellowing, comparedto the modified polyolefins of the prior art. As regards this yellowingfor example, the YI (yellow index, measured according to standards ASTMD-1925 and ASTM E-313) of the polyolefins according to the invention isgenerally less than or equal to 40, or even less than or equal to 30.

The modified polyolefins according to the invention find an advantageousapplication in the preparation of foams, in particular of high-densitypolypropylene foams and high-density polyethylene foams produced byfoaming extrusion. In particular, the modified polyolefins find anadvantageous application in the production of objects made by foamingextrusion, thermoforming or blow-moulding, in particular by 3Dblow-moulding. Another field of application is that of improvingadhesion in compatibilization applications, multilayer applications andsealing applications.

Moreover, the modified polyolefins according to the invention alsoexhibit, in certain cases, adhesive properties that are superior tothose of the unmodified grafted polyolefins. Thus for example, theyexhibit better adhesion in the presence of oils and of fats, on manysubstrates. The maximum stress measured in an adhesion test (testaccording to standard NFT 76-104) with these polyolefins and oilysubstrates (steel sheets, for example) is in fact generally at leastequal to 8 MPa and the breakages observed are generally of adhesive type(according to the definition of standard NFT 76-107). Consequently,these polyolefins are suitable as adhesives, in particular in packagingsfor fatty products (foods, cosmetics, etc.), in tanks and pipes forhydrocarbons (petrol). In the case of the PP-based modified polyolefins,the adhesion on A1 substrates (optionally surface treated) is alsoimproved compared with that of the unmodified grafted PPs (i.e. themaximum stress in the adhesion test is also at least equal to 8 MPa andthe failure is adhesive).

A subject of the present invention is also a polymeric composition thathas many advantages compared with the polymeric compositions of theprior art without having the disadvantages thereof.

To this effect, the invention relates to a polymeric compositioncontaining

-   (A) at least one polymer, and-   (B) at least one modified polyolefin chosen from the modified    polyolefins obtained by the process in accordance with the invention    [process (P)], as described above [modified polyolefins (B1)], And    the modified polyolefins that can be obtained by said process, as    described above [modified polyolefins (B2)].    Thus, the invention relates to a polymeric composition containing-   (A) at least one polymer, and-   (B) at least modified polyolefin chosen from:    -   the modified polyolefins (B1), i.e. the polyolefins grafted with        acid or anhydride groups, modified by a process according to        which these groups are at least partially neutralized with at        least one neutralizing agent comprising an organic salt (1) that        releases an organic acid (I) during the neutralization, and the        organic acid (I) derived from the neutralization of the grafted        polyolefins is reacted with at least one inorganic salt (2)        [process (P)], and    -   the modified polyolefins (B2), i.e. the modified polyolefins        that can be obtained by the process (P), comprising acid or        anhydride groups that are at least partially neutralized by        metal ions, and exhibiting a content of products insoluble in        xylene at 130° C. of less than 1%, an exponential increase in        elongational viscosity as a function of time, and an MFI of less        than or equal to 6 dg/min.

The process (P) that is used to synthesize the modified polyolefins (B1)of the compositions according to the present invention corresponds tothe same characteristics and preferences, whatever the level ofpreference, as those of the process (P) in accordance with theinvention, which is described from the paragraph beginning with “To thiseffect, the present invention relates to a process for modifying agrafted polyolefin” up to the paragraph ending “the preferred stabilizeris 1,3,5-trimethyl-2,4,6-tris(3,5-t-butyl-4-hydroxybenzyl)-benzene”.

Similarly, the modified polyolefins (B2) of the compositions accordingto the present invention correspond to the same characteristics andpreferences, whatever the level of preference, as those of the modifiedpolyolefins (B2) in accordance with the invention which are describedfrom the paragraph beginning with “Consequently, the present inventionalso relates to the modified polyolefins that can be obtained by aprocess as described above” up to the paragraph ending with “the maximumstress in the adhesion test is also at least equal to 8 MPa and thefailure is adhesive”.

The modified polyolefin is preferably chosen from the modifiedpolyolefins (B1).

-   (A) may in particular be:    -   an aromatic polycondensate such as a polyphthalamide, a        polyamide obtained by condensation of metaxylylenediamine and of        at least one diacid, a polyamideimide, an aromatic polyester        such as a liquid-crystal polyester, a polysulphone, a        polyaryletherketone or a polyphenylene sulphide;    -   a polyadduct such as a halogenated polymer, for instance PVC,        PVDC, PVDF and PTFE, a polyvinyl ester, an acrylic polymer, a        polymer of styrene, such as polystyrene, a polymer of an        alkadiene, such as polybutadiene, a polymer of styrene and of an        alkadiene, such as SBS rubber, a styrene homopolymer, or a        non-functionalized polyolefin.

(A) is preferably a non-functionalized polyolefin, i.e. anon-functionalized olefin polymer and, particularly preferably, anon-functionalized linear olefin polymer.

By way of example of linear olefins, mention be made of ethylene,propylene, 1-butene, 1-pentene, 1-hexene, 1-octene and 1-decene.

The linear olefin preferably contains from 2 to 8 carbon atoms,particularly preferably from 2 to 6 carbon atoms, and most particularlypreferably from 2 to 4 carbon atoms. Excellent results have beenobtained when the linear olefin is ethylene and/or propylene.

The non-functionalized polyolefin may in particular be a homopolymer ofthe abovementioned olefins or a copolymer of the abovementioned olefinswith one or more comonomers.

The comonomers are advantageously chosen from the olefins describedabove, from diolefins comprising from 4 to 18 carbon atoms, such as4-vinylcyclohexene, dicyclopentadiene, methylenenorbornene andethylidenenorbornene, 1,3-butadiene, isoprene and 1,3-pentadiene, andfrom styrene monomers such as styrene and alpha-methylstyrene.Preferably, they are chosen from the linear olefins above.

The content by weight of comonomer units in the non-functionalizedpolyolefin of the composition according to the invention isadvantageously less than 50%, preferably less than 30% and particularlypreferably less than 10% by weight.

By way of examples of non-functionalized olefin copolymers, mention maybe made of random copolymers of propylene (>90% by weight) and ofethylene (<10% by weight), such as the copolymer ELTEX® KS.

The non-functionalized polyolefin is particularly preferably selectedfrom homopolymers of the abovementioned olefins, quite particularlypreferably from ethylene homopolymers and propylene homopolymers, andmost preferably from propylene homopolymers, such as the polypropyleneELTEX® HL.

A specific composition in accordance with the invention comprises, aspolymer (A), a non-functionalized polyolefin which is a blockedcopolymer, preferably a blocked copolymer comprising repeat unitsderived from ethylene and/or from propylene. By way of examples of blockcopolymers, mention may be made of AB diblock copolymers and ABAtriblock copolymers, where the A blocks are blocks of polystyrenehomopolymer and the B blocks are blocks of a copolymer composed,firstly, of repeat units derived from ethylene and, secondly, of repeatunits derived from propylene and/or from a diolefin comprising from 4 to18 carbon atoms, such as butadiene, that are optionally hydrogenated(for example, the repeat units derived from butadiene may behydrogenated to butylene repeat units). As regards this specificcomposition according to the invention and, by exception, the content byweight of units formed from comonomers other than ethylene andpropylene, of the non-functionalized polyolefin block copolymer isadvantageously at least 10%, preferably at least 20% by weight; inaddition, it is advantageously less than 75%, and preferably less than50% by weight. An example of this specific composition in accordancewith the invention is a composition comprising, as polymer (A), apolypropylene homopolymer and a styrene-ethylene/butylene-styrene blockcopolymer comprising approximately 30% by weight of styrene (commonlycalled SEBS rubber), and, as modified polyolefin (B), a maleicanhydride-grafted polypropylene homopolymer and a maleicanhydride-grafted SEBS rubber, both modified according to the process inaccordance with the invention.

The weight of (A), relative to the total weight of the composition, isadvantageously greater than 50%, preferably greater than 75%, andparticularly preferably greater than 85%.

The weight of (B), relative to the total weight of the composition, isadvantageously greater than 0.5%, preferably greater than 1%,particularly preferably greater than 2%.

The weight of (B), relative to the total weight of the composition, isadvantageously less than 40%, preferably less than 20%, particularlypreferably less than 10%, and most particularly preferably less than 6%.

The composition according to the invention can be prepared by any knownprocess, in particular processes in solution, processes that take placein a mixer, for example a Brabender® mixer, and processes that takeplace in an extruder, for example a Prism® extruder. Good results areusually obtained if the compositions according to the invention areprepared by a process that takes place in an extruder.

The compositions according to the invention can optionally also containadditives that are usual in polymeric compositions, in particularadditives that are usual in polyolefin compositions, in an amountpreferably ranging up to 10%, particularly preferably up to 5% byweight, relative to the total weight of the composition.

By way of examples of such usual additives, mention may be made ofantioxidants such as sterically hindered phenols, lubricants, fillers,dyes, pigments, nucleating agents, LTV stabilizers, antacids such ascalcium stearate, agents for modifying crystallinity, such as copolymersof ethylene and of n-butyl acrylate or ethyl acrylate,metal-deactivating agents and antistatic agents.

The compositions according to the invention preferably contain from 0.1to 0.5% by weight, relative to the total weight of the composition, of asterically hindered phenol such as1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene andpentaerythritol tetrakis-(3,5-di-t-butyl-4-hydroxyphenylpropionate).

The composition according to the present invention exhibits an overalllevel of properties that is clearly improved compared with that of thecompositions of the prior art. This clear improvement results from theaddition to the polymeric compositions, in particular to thecompositions containing a non-functionalized polyolefin, of a modifiedpolyolefin that is obtained or that can be obtained by the processaccording to the invention. The improved properties may in particular bethe melt strength (exponential increase in elongational viscosity andimproved low MFI, while at the same time maintaining a low content ofcrosslinked polymer), and also the mechanical properties, such as thetensile modulus. In addition, in the case of compositions of PPhomopolymer to which as little as a few percent (for example, 5%) byweight of a PP homopolymer-based modified polyolefin have been added, aclear improvement in mechanical strength has been observed, which isreflected by an increase of close to 10° C. in the deflectiontemperature under load; the behaviour in the VICAT test, the impactstrength and the creep resistance are themselves also substantiallyimproved. Finally, the composition according to the invention alsoexhibits, in certain cases, adhesive properties that are superior tothose of compositions based on non-functionalized polyolefin and free ofmodified polyolefin. Thus, for example, they exhibit better adhesion inthe presence of oils and of fats, on many substrates. In the case ofcompositions containing a non-functionalized PP and a grafted PPaccording to the invention, the adhesion on aluminium supports(optionally surface treated) is also improved compared with that ofcompositions free of grafted PP.

A subject of the present invention is also an article made from apolymer or from a polymeric composition, that exhibits many advantagescompared to the articles of the prior art, without exhibiting thedisadvantages thereof.

To this effect, the invention relates to an article comprising eitherthe composition in accordance with the invention, as described above, ora modified polyolefin chosen from the modified polyolefins obtained bythe process in accordance with the invention [process (P)], as describedabove [modified polyolefins (B1)] and the modified polyolefins that canbe obtained by said process, as described above [modified polyolefins(B2)].

A first preferred choice for the article according to the invention isthat made from glass fibres, natural fibres and metal wires sized with alayer of the composition or of the modified polyolefin, and also frommetal surfaces and non-metal surfaces coated with a layer of thecomposition or of the modified polyolefin.

By way of example of non-metal surfaces, mention may be made of cementsurfaces, glass surfaces, stone surfaces and polymer surfaces.

A second preferred choice for the article according to the invention isthat made from tubes, films, sheets, fibres, foams and blow-mouldedhollow bodies made of the composition or of the modified polyolefin.

By way of examples of blow-moulded hollow bodies, mention may be made ofbottles.

The tubes are advantageously intended for the oil industry, for theconstruction industry or for the automobile industry.

The films may in particular be food-related films that are sealable in afatty medium or films that can be printed with aqueous inks.

A third preferred choice for the article according to the invention isthat of a part for an automotive vehicle, selected from fuel tanks, fuelpipes, bumpers and dashboards.

The article in accordance with the invention has many advantages. Itusually has a smaller thickness or is lighter than the articles of thesame nature of the prior art. It exhibits resistance to soiling, toscratching, to abrasion and to graffiti. When the article according tothe invention is a film, the latter exhibits high tear resistance andcan be bonded in soiled environments.

Finally, a last aspect of the invention envisages the use either of thecomposition in accordance with the present invention, or of a modifiedpolyolefin chosen from the modified polyolefins obtained by the processin accordance with the invention [process (P)], as described above[modified polyolefins (B1)] and the modified polyolefins that can beobtained by said process, as described above [modified polyolefins(B2)], as an agent for compatibilization and/or for dispersion of apolyolefin with a polymer or a filler that is incompatible with thepolyolefin.

By way of examples of polymers that are incompatible with thepolyolefins, mention may be made of epoxy resins, fluorinated resins,and in particular poly(vinylidene fluoride), polyamides and polyesters.

Preferably, the composition according to the invention or the polyolefinchosen as indicated above is used as an agent for compatibilizationand/or for dispersion of a polyolefin in an epoxy resin.

Incompatible fillers are, for example, natural fibres, such as flax,hemp, jute and cellulose, and also glass fibres, glass, silica, talc,calcium carbonate and carbon black. Metal substrates are, for example,steel or aluminium.

The following examples are intended to illustrate the invention without,however, limiting the scope thereof.

REFERENCE EXAMPLE 1 (NOT IN ACCORDANCE WITH THE INVENTION) AND EXAMPLE 2(IN ACCORDANCE WITH THE INVENTION) Propylene (PP)-Based GraftedPolyolefins Neutralized with Zn Acetate

The following were used:

-   -   a Priex® 20070 resin, a polypropylene chemically modified by        Solvay. It is a PP grafted with maleic anhydride in a proportion        of 0.1% by weight, which has an MFI_(2.16 kg, 230° C.) of 64        g/10 min; solutions of Zn acetate (Zn(Ac)₂) and of Na₂CO₃ at 200        g/l, in respective amounts of 3 mol. eq. (molar equivalents        relative to the number of carboxylic acid functions of the        resin) for the Zn(Ac)₂ and of 0 mol. eq. (Counter-example 1) and        2 mol. eq. (Example 2) for the Na₂CO₃;    -   a Clextral model BC 21 extruder, which is a co-rotating        twin-screw extruder, diameter 25 mm and length 1000 mm (L/D=40).        The barrel consists of 10 independent zones (Z1 to Z10) and also        a converging flow region and a die;    -   a screw speed of 200 rpm, a throughput of 10 kg/h and the        following temperature profile: Z1 (resin feed): 70° C.; Z2: 170°        C.; Z3 (melting) and Z4 (injection Zn(Ac)₂): 200° C.; Z5 to Z8        (reaction, degassing at atmospheric pressure, reaction,        degassing under vacuum at a set pressure of 2 mbar): 240° C.;        Z9: 230° C.; Z10: 220° C.; converging flow region and die: 220°        C.;    -   high-pressure injectors for the injection, respectively, of        Zn(Ac)₂ in Z4 and of Na₂CO₃ in Z7, where appropriate (example        2).

The elongational viscosity of the modified resins obtained wasdetermined using a rheometer sold by Rheometrics under the name RME(Rheometrics Elongational Rheometer For Melts). The sample (55×9×2 mm)was obtained by extrusion and was subjected to a relaxation procedureand then to measurement of the variation, at 190° C., in elongationalmelt viscosity (expressed in kPa·s) as a function of time (expressed ins) for an elongation rate (expressed in s⁻¹) of 1.

In the two cases (Counter-example 1 and Example 2), resins exhibiting anelongational hardening (the elongational viscosity ranging from 0 tomore than 1000 kPa·s after 2 to 3 s) were obtained.

In addition, the content of products insoluble in xylene at 130° C.(determined by the method described above) was measured for these tworesins, and is less than 1 percent.

The MFI (2.16 kg, 230° C.) is 8.6 dg/min for the resin derived fromCounter-example 1, and 0.5 dg/min for the resin derived from Example 2.In addition, the latter has a whiter appearance and a lack of aceticacid odour compared with the former.

Reference example 1 was repeated, increasing the dose of Zn(Ac)₂ tovalues of 4 and 5 mol. eq., respectively, but the value of the MFIremained substantially the same.

REFERENCE EXAMPLE 3 AND EXAMPLES 4 AND 5 (IN ACCORDANCE WITH THEINVENTION) Propylene (PP)-Based Grafted Polyolefins Neutralized with NaLactate (NaLac)

The same starting resin and the same experimental parameters as in theprevious examples were used. However, the neutralizing agent was thistime NaLac (sodium lactate: mixture of D- and L-isomer from Acros: 256.4ml of solution at 60% by weight per litre of aqueous solution), used ina proportion of 5 mol. eq. The Na₂CO₃ was used in a proportion of 0 mol.eq. (Counter-example 3), 1 mot. eq. (Example 4) and 2 mol. eq. (Example5). The MFI (2.16 kg, 230° C.) of the modified resins obtained was 23.2dg/min, 5 dg/min and 0.5 dg/min, respectively. These resins all exhibitelongational hardening and have a content of products insoluble inxylene at 130° C. of less than 1%.

REFERENCE EXAMPLE 6 AND EXAMPLES 7 AND 8 (IN ACCORDANCE WITH THEINVENTION) Propylene (PP)-Based Grafted Polyolefins Neutralized with ZnAcetate

These examples were undertaken with reactants and operating conditionsidentical to those of Examples 1 and 2.

The amounts of reactants used and also the results obtained appear inthe table below:

Ex. Zn(Ac)₂ Na₂CO₃ Zn N MFI T_(m) T_(c) PIO2 Odour C6 3.0 0 2 65 9.8 163113 >60 1 7 2.7 1.7 1.9 68 1.7 164 122 >60 0 8 2.5 1.5 1.7 59 3.3 165122 >60 0 In this table: Zn(Ac)₂ is the amount of Zn(Ac)₂ used,expressed in mol. eq. Idem for Na₂CO₃ Zn is the content of Zn in themodified resin, measured by X-ray fluorescence and expressed in g/kg Nis the percentage of neutralized MA functions, measured by IRspectrometry The MFI is measured at 230° C., under 2.16 kg, and isexpressed in dg/min T_(m) and T_(c) are, respectively, the melting pointand the crystallization temperature, measured by DSC PIO2 is theoxidation resistance as defined above Odour: 0 = no odour, 1 = slightodour; 2 = pronounced odour.

The resins derived from these examples all exhibit elongationalhardening and have a content of products insoluble in xylene at 130° C.of less than 1%.

The resin derived from Example 7 was subjected to supplementarydeterminations: its modulus E is 2206 MPa, its YI is 29.4, and its DTULis 125° C. under 0.445 MPa and 64° C. under 1.8 MPa (see definitions andmethods for measuring these parameters, above), and it hag a favourableorganoleptic assessment (taste tests after soaking of water in modifiedpolyolefin-based containers, by comparison with a reference water; thefavourable grade corresponds to a zero or weak taste).

REFERENCE EXAMPLE 9 AND EXAMPLES 10 TO 15 Ethylene (PE)-Based GraftedPolyolefins Neutralized with NaLac

These examples were undertaken with reactants and operating conditionsidentical to those of Examples 3 to 5, but with a Priex® 12030 resinfrom Solvay as starting resin. It is an HDPE grafted with maleicanhydride in a proportion of 0.14% by weight, that exhibits anMFI_(5 kg, 8/2, 190° C.) of 30 g/10 min.

The amounts of reactants used and also the results obtained appear inthe table below:

Ex. NaLac Na₂CO₃ Na N MFI T_(m) T_(c) PIO2 Odour C9 0.5 0 — — 20.0 — — —— 10 0.5 1 — — 2.4 — — — — 11 0.75 1 — — 2.4 — — — — 12 1 1 — — 2.5 — —— — 13 0.5 1.5 — — 1.8 — — — — 14 0.5 1.6 1.4 64 1.4 135 113 >60 0 150.4 0.5 0.7 43 4.3 135 113 >60 0 In this table: NaLac is the amount ofNaLac used, expressed in mol. eq. Idem for Na₂CO₃ Na is the content ofNa in the modified resin, measured by X-ray fluorescence, and expressedin g/kg N is the percentage of neutralized MA functions, measured by IRspectrometry The MFI is measured at 230° C., under 5 kg, and isexpressed in dg/min T_(m) and T_(c) are, respectively, the melting pointand the crystallization temperature, measured by DSC PIO2 is theoxidation resistance as defined above Odour: 0 = no odour; 1 = slightodour; 2 = pronounced odour.

The resins derived from Examples 14 and 15 were subjected tosupplementary determinations, which showed that:

-   -   they both exhibit elongational hardening, they have a context of        products insoluble in xylene at 130° C. of less than 1%, and        they have a favourable organoleptic assessment;    -   they have, respectively, a modulus E of 1009 and 1033 MPa and a        YI of 27 and 22.9.

EXAMPLE 16 (IN ACCORDANCE WITH THE INVENTION) Propylene (PP)-BasedGrafted Polyolefin Neutralized with Sodium Lactate (NaLac)

A Priex® 20015 resin, which is a polypropylene homopolymer chemicallymodified by Solvay, was used as starting resin. It is a PP grafted withmaleic anhydride in the proportion of 0.5% by weight, that exhibits anMFI_(2.16 kg, 230° C.) of 15 g/10 min.

The neutralizing agent was NaLac (sodium lactate: mixture of D- andL-isomer from Acros; 256.4 ml of solution at 60% by weight per litre ofaqueous solution), used in a proportion of 5 mol. eq.

The Na₂CO₃ was used in a proportion of 2 molar equivalents.

The experimental parameters applied were the same as those applied forthe previous examples (cf. Examples 1 and 2 for details).

The MFI (2.16 kg, 230° C.) of the modified resin thus obtained was 1g/10 min, and it had a sodium content of 0.88 g/kg. Its melting pointwas 167° C.

REFERENCE EXAMPLE 17 (NOT IN ACCORDANCE WITH THE INVENTION) AND EXAMPLE18 (IN ACCORDANCE WITH THE INVENTION) Composition Comprising aNon-Functionalized Polypropylene Respectively without/with AdditiveConsisting of Propylene (PP)-Based Grafted Polyolefin Neutralized withSodium Lactate (NaLac)

A composition in the form of granules, composed of polypropylenehomopolymer Eltex® P HL and of a sterically hindered phenol stabilizer(composition sold by BP) was used as reference composition, hereinaftercomposition (CR17). This composition had an MFI (2.16 kg, 230° C.) of2.5 g/10 min, a melting point of 161° C. and a density of 900 kg/m³.

A composition in accordance with the invention, hereinafter composition(CI18), composed of 95% by weight of the composition (CR17) and of 5% byweight of the PP-based grafted polyolefin neutralized with NaLac,synthesized in Example 16, was prepared. To this effect, a Prism®co-rotating twin-screw extruder, diameter 15 mm and length 24 cm (i.e. alength to diameter ratio of 16), the barrel of which consists of 2independent zones (Z1 and Z2) and also a converging flow region and ahole die, was used. A screw speed of 200 rpm and a throughput of 2 kg/hwere applied, and the temperature profile was as follows: Z1 (feedzone); 230° C.; Z2: 230° C.; converging flow region and die: 230° C.

Tensile Test at 23° C.

This test was carried out according to standards ISO 527-1 and 2; themodulus speed was 1 mm/min; the test speed was 50 mm/min; the distancebetween the tools was 115 mm; the standard gauge length was 50 mm; thetest piece type was the ISO 1B (115) type; the load cell was of the “1kN tension—without an oven” type; the extensometer was a Zwick Multisensand Traverse sensor; the temperature was 23° C.

The results given in the following table were obtained:

Composition Composition (CR17) (CI18) Modulus 0.05-0.25% (in MPa) 17492127 Yield elongation (in %) 8.5 7.0 Yield stress (in MPa) 37.0 39.3Tensile strength (in MPa) 14.9 24.3

Determination of the Deflection Temperature Under Load (DTUL)

This determination was carried out according to standard ISO 75-2(9/1993) under a load either of 0.45 MPa, or of 1.8 MPa. An increase intemperature of 120° C./h was effected; the preload was 50 g; the heattransfer fluid used was silicone oil; test pieces that had beeninjection moulded, trimmed and cut to a length of 120±10 mm were used;the test pieces were placed on the side; the distance between thesupports was 100±2 mm.

The results given in the table below were obtained:

Composition Composition (CR17) (CI18) DTUL under a load of 0.45 MPa (in° C.) 110 119 DTUL under a load of 1.8 MPa (in ° C.) 59 68

VICAT test. The VICAT test was carried out according to standard ISO 306(1987). Both for the 10 N VICAT measurement and for the 50 N VICATmeasurement, the penetration was 1 mm.

The results given in the table below were obtained:

Composition Composition (CR17) (CI18) Softening temperature 157 159 10 NVICAT (in ° C.) Softening temperature 101 107 50 N VICAT (in ° C.)

Determination of Impact Strength—Instrumented Falling Weights (IFW)Test.

The IFW test was carried out according to standard ISO 7765-2. Thetemperature was 23° C.; the theoretical energy and speed of the strikerwere, respectively, 247.5 J and 4.43 m/s; the mass of the striker was25.24 kg; the drop height was 1 m; the diameters of the striker and ofthe support were, respectively, 20 and 40 mm.

The results given in the table below were obtained:

Composition Composition (CR17) (CI18) Maximum strength (in N) 445 688Displacement at maximum strength (in mm) 3.3 5.2 Energy at maximum force(in J) 0.78 1.73 Toughness (in J/mm) 0.47 0.87

Creep test. This test was carried out under a stress of 10 MPa on anISO1A test piece and at a temperature of 23° C.

The results given in the table below were obtained:

Composition Composition (CR17) (CI18) Modulus after 0.01 h (in MPa) 17561914 Modulus after 0.1 h (in MPa) 1420 1561 Modulus after 1 h (in MPa)1113 1254 Modulus after 10 h (in MPa) 787 918 Modulus after 1 day (inMPa) 680 807 Modulus after 100 h (in MPa) 548 652

EXAMPLE 19 (IN ACCORDANCE WITH THE INVENTION) Propylene (PP)-BasedGrafted Polyolefin Neutralized with Sodium Lactate (NaLac)

A Prim® 20093 resin, which is a polypropylene homopolymer chemicallymodified by Solvay, was used as starting resin. It is a PP grafted withmaleic anhydride in a proportion of 0.26% by weight, that has aweight-average molecular mass of 75 000.

The NaLac neutralizing agent and the Na₂CO₃ were used in the same amountand in the same way as in Example 16.

The experimental parameters applied were also the same as those appliedfor the previous examples.

The MFI (2.16 kg, 230° C.) of the modified resin thus obtained was 1.4g/10 min, and it had a sodium content of 6.6 g/kg. Its melting point was135° C.

REFERENCE EXAMPLE 20 (NOT IN ACCORDANCE WITH THE INVENTION) AND EXAMPLE21 (IN ACCORDANCE WITH THE INVENTION) Composition Comprising aNon-Functionalized Polypropylene Respectively with/without AdditiveConsisting of Polypropylene (PP)-Based Grafted Polyolefin Neutralizedwith Sodium Lactate (Nalac)

A composition (CR20) identical in all respects to the composition (CR17)was used as reference composition.

A composition in accordance with the invention, hereinafter composition(CI21), composed of 95% by weight of the composition (CR20) and of 5% byweight of the PP-based grafted polyolefin neutralized with NaLac,synthesized in Example 19, was prepared.

Test to Evaluate the Cohesion and the Adhesion on Various Substrates.

These tests were carried out according to standard NP' T 76-104.

The shear test pieces were prepared by compression moulding, at atemperature of 230° C. and under a pressure of 20 bar:

-   -   between two aluminium plates immersed beforehand for 10 minutes        in a sulphochromic acid bath, or    -   between two aluminium plates immersed beforehand for 10 minutes        in an alkaline bath, or else    -   between two steel plates immersed beforehand for 10 minutes in a        sulphochromic acid bath.

The tensile strength of the shear test pieces was determined in a sheartest carried out using an MTS 50LP machine equipped with a 50 kN sensor.

Tensile strength (in MPa) for the substrate/bath couple = CompositionComposition (CR20) (CI21) Aluminium substrate/ 1 7 sulphochromic acidbath Aluminium substrate/ 0.4 4 alkaline bath Steel substrate/ 2 7sulphochromic acid bath

EXAMPLES 22 TO 24 (IN ACCORDANCE WITH THE INVENTION) Grafted, BlockCopolymer Polyolefins Neutralized with Sodium Lactate (NaLac)

The following were used:

-   -   a Kraton® FG1901X styrene-ethylene/butylene-styrene block        copolymer resin containing approximately 30% by weight of        polystyrene blocks, grafted with maleic anhydride, sold by        Kraton Polymers. According to determinations made by us, the        resin used had a degree of maleic anhydride grafting of        approximately 1.1% by weight and an MFI_(2.16 kg, 230° C.) of        6.2 g/10 min,    -   solutions of sodium lactate and of sodium carbonate at 200 g/l,        in respective amounts of 0.129 (Example 22), 0.258 (Example 23)        and 0.323 (Example 24) theoretical mol. eq. (molar equivalents        relative to the number of carboxylic acid functions of the        resin) for, firstly, the sodium lactate, and of 0.258 (Example        22), 0.517 (Example 23) and 0.647 (Example 24) theoretical mol.        eq. (molar equivalents relative to the number of carboxylic acid        functions of the resin) for, secondly, the Na₂CO₃,    -   a Clextral model BC 21 extruder, which is a co-rotating        twin-screw extruder, diameter 25 mm and length 1200 mm (L/D=40),        with a barrel consisting of 12 independent zones (Z1 to Z12) and        also of a converging flow region and a die,    -   a screw speed of 300 rpm, a throughput of 3 kg/h and the        following temperature profile: Z1 (resin feed): 100° C.; Z2 to        Z4 (melting): Z2: 200° C.; Z3: 220° C.; Z4: 230° C.; Z5        (co-injection of NaLac Na₂CO₃): 220° C.; Z6 to Z10 (reaction,        degassing at atmospheric pressure, reaction, degassing under        vacuum at a set temperature of 2 mbar): 240 except Z10: 220° C.;        Z11 and Z12: 220° C.; converging flow region and die: 220° C.,    -   a high pressure injecting device for co-injecting the        NaLac+Na₂CO₃ in Z5.

Modified resins having an MFI_(21.6 kg, 230° C.) of 31 g/10 min forExample 22, of 7.7 g/10 min for Example 23 and of 3.2 g/10 min forExample 24 were obtained.

It was noted that, the greater the increase in the close ofNaLac+Na₂CO₃, the greater the decrease in the yellow index of thepolymer obtained (the yellow index on granules according to standardsASTM D-1925 and ASTM E-313 was 38 for Example 22, 28 for Example 23, and27 for Example 24).

The Na contents (measured by FX) were, respectively, 2.0 g/kg forExample 22, 3.9 g/kg for Example 23, and 4.6 g/kg for Example 24.

EXAMPLES 25 TO 27 (IN ACCORDANCE WITH THE INVENTION) CompositionsComprising a Grafted Block Copolymer Polyolefin Neutralized with SodiumLactate (NaLac)

Compositions in accordance with the invention, hereinafter compositions(CI22 to CI24) were prepared, which compositions were composed of:

-   -   57% by weight of polypropylene homopolymer Eltex® P HL        stabilized with sterically hindered phenol (sold by BP), having        an MFI_(2.16 kg, 230° C.) of 2.5 g/10 min, a melting point of        161° C. and a density of 900 kg/m³,    -   3% by weight of the chemically modified grafted polypropylene        homopolymer of Example 16,    -   3% by weight of the polymer synthesized in Example 22 (CI22), 23        (CI23) or 24 (CI24), and    -   37% by weight of polymer Kraton® G 1652, which is a        styrene-ethylene/butylene-styrene non-functionalized block        copolymer containing approximately 30% by weight of polystyrene        blocks, sold by Kraton Polymers.

The compositions thus prepared exhibit an advantageous combination ofproperties.

1-25. (canceled)
 26. A modified polyolefin having a plurality of atleast one of grafted acid groups and grafted anhydride groups that areat least partially neutralized by metal ions, wherein the modifiedpolyolefin further has: a content of products insoluble in xylene at130° C. of less than 1%; an exponential increase in elongation viscosityas a function of time; and an MFI of ≦6 dg/min; and wherein the modifiedpolyolefin is obtained by a process comprising: at least partiallyneutralizing at least one of acid groups and anhydride groups graftedonto a first polyolefin with at least one neutralizing agent comprisingan organic salt (1), wherein the organic salt (1) releases an organicacid (I) during the neutralizing, reacting the organic acid (I) releasedduring the neutralizing of the first polyolefin with at least oneinorganic salt (2) to form an inorganic acid (II) and an organic salt(3), and eliminating the inorganic acid (II) by decomposition to form agas.
 27. The modified polyolefin according to claim 26, having ayellowness index measured according to ASTM D-1925 and ASTM E-313 ofless than
 40. 28. The modified polyolefin according to claim 26 havingno odor.
 29. A polymeric composition, comprising: (A) at least onesecond polymer; and (B) at least one modified polyolefin according toclaim
 26. 30. A polymeric composition, comprising: (A) at least onesecond polymer; and (B) at least one modified polyolefin according toclaim
 28. 31. The modified polyolefin of claim 26, wherein the firstpolymer is selected from the group consisting of an ethylene polymergrafted with maleic anhydride and a propylene polymer grafted withmaleic anhydride.
 32. The modified polyolefin according to claim 26,wherein the first polymer is at least one selected from the groupconsisting of a non-functionalized ethylene polymer and anon-functionalized propylene polymer.
 33. The composition according toclaim 29, wherein the weight of (A) relative to the total weight of thecomposition is greater than 75%.
 34. An article comprising thecomposition according to claim
 29. 35. The article according to claim34, selected from the group consisting of a glass fiber, a naturalfiber, a metal wire sized with a layer of the modified polyolefin, ametal surface coated with a layer of the modified polyolefin and anon-metal surface coated with the modified polyolefin.
 36. The articleaccording to claim 34, selected from the group consisting of a tube, afilm, a sheet, a fiber, a foam and a blow-molded hollow body.
 37. A partfor an automotive vehicle made from the modified polyolefin according toclaim 26, wherein the part is selected from the group consisting of afuel tank, a fuel pipe, a bumper and a dashboard.
 38. A modifiedpolyolefin comprising at least one of grafted acid groups and graftedanhydride groups, wherein the modified polyolefin is obtained by aprocess that includes at least partially neutralizing the grafted acidgroups and grafted anhydride groups with at least one neutralizing agentcomprising an organic salt (1) that releases an organic acid (I) duringthe neutralization and wherein the organic acid (I) derived from theneutralization of the grafted acid groups and grafted anhydride groupsis reacted with at least one inorganic salt (2), wherein the graftedacid and anhydride groups are neutralized by metal ions, and wherein themodified polyolefin has: a content of products insoluble in xylene at130° C. of less than 1%; an exponential increase in elongationalviscosity as a function of time; and an MFI of less than or equal to 6dg/min.